Endothelial cell Ca²⁺ is increased by melanoma cell adhesion

The signal transduction mechanisms that control tumor cell-endothelium adhesion and tumor cell migration are still largely undefined. We examined the effect of metastatic murine melanoma cell (B16/ G3.26) adhesion on cytosolic [Ca²⁺] (Ca(i)) of bovine pulmonary artery endothelial cells (BPAECs), loaded with the membrane-permeant ester form of the fluorescent Ca²⁺ indicator indo-1. Indo-1 was excited at 350 nm and the ratio of emitted indo-1 fluorescence at 410/490 nm was used as an index of Ca(i),. Upon contact between melanoma and endothelial cells there was a rapid increase in endothelial cell Ca(i) which exhibited a partial recovery toward control. BPAECs contact with 8 μm inert beads did not elicit an increase in Ca. In conclusion, melanoma-endothelium contact modulates endothelial cell Ca(i); homeostasis.